1. Field of the Invention
The present invention relates generally to Ethernet systems and, more particularly, to a system and method for using a link energy/sync pulse in physical layer devices (PHYs) having a silent channel/interface in energy efficient Ethernet (EEE).
2. Introduction
Energy costs continue to escalate in a trend that has accelerated in recent years. Such being the case, various industries have become increasingly sensitive to the impact of those rising costs. One area that has drawn increasing scrutiny is the IT infrastructure. Many companies are now looking at their IT systems' power usage to determine whether the energy costs can be reduced. For this reason, an industry focus on energy efficient networks has arisen to address the rising costs of IT equipment usage as a whole (i.e., PCs, displays, printers, servers, network equipment, etc.).
In designing an energy efficient solution, one of the considerations is the traffic profile on the network link. For example, many network links are typically in an idle state between sporadic bursts of data, while in other network links, there can be regular or intermittent low-bandwidth traffic, with bursts of high-bandwidth traffic. An additional consideration for an energy efficient solution is the extent to which the traffic is sensitive to buffering and latency. For example, some traffic patterns (e.g., HPC cluster or high-end 24-hr data center) are very sensitive to latency such that buffering would be problematic. For these and other reasons, applying energy efficient concepts to different traffic profiles would lead to different solutions. These varied solutions can therefore seek to adapt the link, link rate, and layers above the link to an optimal solution based on various energy costs and impact on traffic, which itself is dependent on the application.
One example of an EEE solution is a low power idle (LPI) mode. In general, LPI relies on turning the active channel silent when there is nothing to transmit. When data is transmitted, it is transmitted at full PHY capacity. Energy is thereby saved when the link is off. While this low power idle mode can save the most power, what is needed is a mechanism that ensures that a cable unplug can be detected remotely in a timely manner and that a frequency lock is maintained.